The present invention relates to preserved food products and to methods of preservation. In particular, the invention relates to the use of biocontrol approaches for the preservation of food products such as heat-treated food products.
Preservation of food products can be achieved using a variety of approaches. Physical manipulations of food products that have a preservative effect include, for example, freezing, refrigerating, cooking, retorting, pasteurizing, drying, vacuum packing and sealing in an oxygen-free package. Some of these approaches can be part of a food processing operation. Food processing steps preferably are selected to strike a balance between obtaining a microbially-safe food product, while producing a food product with desirable qualities.
Furthermore, additives can be combined with the food product as preservatives. Although some food additives can be effective at providing a microbially safe food product, some consumers disfavor added non-natural chemical preservatives. Some chemical preservatives such as citric acid and lactic acid are perceived to be natural and correspondingly more desirable. Some natural preservatives may be effective at providing a microbially safe food product, but at sufficient concentrations to be effective, they can adversely affect the taste and texture of many food products, such as dough products and alimentary pastes.
Due to the time constraints of modern life, there is an increasing demand for high quality food products that are simple to prepare. To produce some of the preferred products, certain effective and long used preservation techniques such as drying may not be desirable. Generally, these food products are preserved by refrigeration. Also, the products generally are pasteurized prior to or at the time of packaging. Thus, a suitable combination of preservation methods include a heating step and a subsequent refrigeration step.
Even though certain food products are pasteurized, certain toxic bacteria form spores that resist destruction by pasteurization. In addition, to reduce the oxidation of the food during storage, the food generally is stored in the absence of oxygen. Many toxic, spore forming bacteria are obligate anaerobic or functional anaerobes.
While refrigeration generally is an effective preservation approach, the products are vulnerable to mishandling in the form of temperature abuse or packaging abuse. In particular, temperature abuse resulting from an improper storage temperature can result in the growth of harmful bacteria from spores. Subsequent proliferation of the harmful bacteria can cause illness to the consumer if the product is later consumed. If the products are subjected to temperature abuse, the growth of harmful bacteria may or may not produce visible signs of spoilage.
Thus, the quality of the product consumed by the ultimate consumer depends on circumstances beyond the control of the producer. In particular, the wholesale and retail distributors should store the products under properly refrigerated conditions. Similarly, the consumer should store and prepare the product in the prescribed manner prior to consumption. Since the products are subject to improper handling, many commercial food products include an added food preservative, to further assure the microbial safety of the food product after it has been manufactured and leaves the control of the manufacturer.
While toxic bacteria are to be avoided, certain bacteria are nontoxic or even beneficial. These nonpathogenic microorganisms form the basis of biocontrol preservation, another type of food preservation system. Biocontrol preservation generally describes the use of nonpathogenic microorganisms and/or their products to inhibit or control pathogenic or toxin-producing microorganisms in food products. Thus, the selected microorganisms replace added chemical preservatives.
The most familiar form of biocontrol preservation is found in fermented food products, such as yogurt. The microorganisms used to ferment yogurt provide not only the desired taste and texture of yogurt but also produce metabolites that inhibit the growth of other microorganisms.
The use of biocontrol preservation also can be used in non-fermented foods, such as milk, meat and meat products, fruits, vegetables and liquid whole eggs. In a fermentation process, a selected microorganism assists with the production of the food product. For example, see Tanaka et al., xe2x80x9cPlant Trials of Bacon Made with Lactic Acid Bacteria, Sucrose and Lowered Sodium Nitrite,xe2x80x9d Journal of Food Protection, 48:679-686 (August 1985). In other forms of biocontrol preservation, the effects of the added microorganisms can be observed only if the food product has been subjected to temperature or other abuse.
Nonharmful bacteria useful for biocontrol preservation, however, generally do not form spores. Therefore, the desirable bacteria generally are killed during a pasteurization or cooking process. As a result, a pasteurization/cooking step tends to eliminate the nonharmful bacteria while allowing for the possible survival of a small number of potentially harmful spore forming bacteria.
In a first aspect, the invention pertains to a food product comprising a hydrated edible food item and a quantity of dry, nontoxic microorganisms.
In another aspect, the invention pertains to a food product comprising a pasteurized food item and live cultures of nontoxic bacteria sealed within a container in an anaerobic environment.
In another aspect, the invention features a method of preserving a food product comprising heating the food product, the food product comprising dried microorganisms.